Fireflies and Whale Sharks, A Fascinating Web of Life

I arrived riverside at dusk in Donsol, an island town in the Philippines. The world was just taking on its magical evening spell as our boat pulled away from the pier and headed up the river. The night itself was spectacular—no moon, a million stars, and the hush of the river with only the sound of the sputtering motor as we glided along. Soon we cut power and our boatman poled us towards shore.

As we neared the riverbank, I detected a faint twinkling in the trees. The flashing grew more intense until it became a swirl of tiny rotating lights—fireflies! But these were like not like fireflies I’d ever seen: they flashed both on their own and also together. The sight was mesmerizing—like strings of dancing white Christmas lights. Looking up into the trees, it was hard to tell stars from fireflies.

As we watched this firefly dance, our boatman softly said, “Now put your hand in the water”…and we did. We expected merely to feel the river’s warmth compared to the now chilly night air. Instead, we were met with yet another treat—light was emitted and a bioluminescence was created by our fingers as they moved through the water.

Our boat moved slowly up river to an even larger swarm of fireflies. We marveled again at the sheer beauty and let our eyes go from the stars to the fireflies to the glowing water trailing our hands.

After a while, the boat turned around and we headed back toward the pier. It was an oddly melancholy trip back down the river. I had a sense that I was leaving something very special behind that I may not ever encounter again. A trifecta of nature’s sparkle left twinkling on the river.

Connection Between Fireflies, Whale Sharks and Mangrove Forests

The fireflies I saw that night congregate in huge colonies to feed in mangrove trees along the riverbanks. Mangroves are significant because they keep the rivers healthy and release important nutrients into the water. These nutrient-rich waters feed microscopic plankton—the source of the bioluminescence.

Out where the river meets the bay of Donsol, large masses of plankton can be found. Whale sharks gather in schools there to feed on the plankton.

Donsol attracts huge numbers of whale sharks compared to other places in the world. As a result, locals benefit from a booming ecotourism industry. WWF has helped with whale shark tourism since 1998. Programs have created jobs and provided a seasonal but steady source of income for the community.

In 2011, WWF spearheaded an effort to plant 10,000 mangrove seedlings. The mangroves will enhance and protect habitat shared by fireflies and whale sharks. By restoring mangrove forests, WWF keeps rivers healthy, ensures habitat for fireflies and food for whale sharks. In turn, fireflies and whale sharks attract tourists and generate important income for local communities.

Fireflies light up the night sky from mangrove trees along the Ogod River. The river is located near the town of Donsol in the Philippines.

Here a man is planting mangroves. Mangroves are important because they are nurseries for young fish and protect coastal areas from storm surges.